Conventionally, an ultraviolet (UV) curable ink that is cured by radiation of UV light is used as an ink for sheet-fed offset printing. Furthermore, a UV curable resin is used as an adhesive around Flat Panel Display (FPD) such as a liquid crystal panel or an organic Electro Luminescence (EL) panel. To cure the UV curable ink or UV curable resin, generally, a UV light illuminating apparatus that irradiates UV light is used.
As the UV light illuminating apparatus, a lamp-type illuminating apparatus using a high pressure mercury lamp or a mercury xenon lamp as a light source has been long known, but recently, in keeping with the demand for reduced power consumption, a longer service life, and a compact device, a UV light illuminating apparatus using Light Emitting Diode (LED) as an alternative to a traditional discharge lamp for a light source is developed.
The UV light illuminating apparatus using LED as a light source is disclosed by, for example, Patent Literature 1. The UV light illuminating apparatus disclosed by Patent Literature 1 is equipped with a plurality of light illuminating modules, each having a light illuminating device on which a plurality of light emitting devices (LEDs) is mounted. The plurality of light illuminating modules is lined up in a row, and is configured to irradiate UV light of a line shape to a predetermined area of an object to be illuminated placed facing the plurality of light illuminating modules.
If LED is used as a light source as described above, a majority of power inputted is converted to heat, resulting in lower light emitting efficiency and a shorter service life caused by heat generated from the LED itself, so coping with the heat is at an issue. Thus, the UV light illuminating apparatus disclosed by Patent Literature 1 employs the design for forced radiation of heat generated from the LED by placing a member for heat radiation on the surface opposite to each light illuminating device.
The member for heat radiation disclosed by Patent Literature 1 is based on so-called air cooling involving cooling down by a flow of coolant, but because pipe installation for coolant is needed, the device itself increases in size or there is a need to prevent leaks. Accordingly, air cooling-based heat radiation with high efficiency using heat pipe is proposed (for example, Patent Literature 2).
A light illuminating apparatus disclosed by Patent Literature 2 has heat pipe and a plurality of heat radiating fins that is inserted into and connected to the heat pipe, on the surface side opposite to a light emitting module having a plurality of light emitting devices (LEDs) mounted thereon, and employs the design for transferring heat generated from the LEDs through the heat pipe and radiating the heat in air from the heat radiating fins.